Throat plate



July 16, 1968 5, s n- Q 3,392,549

' THROAT PLATE Filed June 18, 1965 /5 I WA-11011111111 4 7d INVENT OR Mm, M,

ATTORNEY5 United States Patent Office 3,392,549 THROAT PLATE Gus T. Smith, Paducah, Ky., assignor to Ace Engineering Co., Paducah, Ky., a corporation of Kentucky Filed June 18, 1965, Ser. No. 465,018 4 Claims. (Cl. 66-125) This invention relates to the art of guides for running strands of yarn and is concerned more particularly With an improved throat plate for circular knitting machines.

The provision of durable guides for rapidly moving strands of filamentitious textile material is hampered by the tendency of the yarn in time to erode the yarn-engaging surface of the guide. Synthetic strands, such as nylon, of relatively fine denier are particularly prone to produce severe wear of the guide surface. The problem is all the more acute in the case of throat plates for circular knitting machines where the yarn passes over the yarnengaging edge of the plate at a sharp, compound angle. Thus, it is by no means uncommon for the yarn to produce after several weeks of operation a hair-line slit of one-eighth inch or greater depth in the corner of the channel of the plate at the yarn-engaging edge. Such a fine slit tends to abrade the running strand, resulting in loose filaments and other undesirable damage to the yarn which ultimately leads to breakdown during the operation of the machine, requiring replacement of the throat plate at considerable expense.

The seriousness of this problem has led a number of perons in the art to propose modifications of the normal construction of the throat plate that would hopefully constitute a solution. One of the more successful of these proposals is described and claimed in my earlier Patent 3,095,718, issued July 2, 1963, according to which a front section of the throat plate is replaced by a correspondingly shaped piece of wear-resistant ceramic material attached to the remainder of the plate by means of a tongue and grooved connection maintained against separation by locking pins. The arrangement of my prior patent has proved eminently satisfactory for use with machines feeding a single strand to the needles or at the main feed position of multi-feed machines. In a single feed circular knitting machine, yarn is fed to the needles from a single point on the circular locus defined by the needle bed to produce a single course of knitted stitches upon each revolution of the cylinder carrying the needle bed. Only a single strand of yarn is fed to the needles at a time for active knitting, even though more than one strand may be employed during the over-all operation to produce a pattern or some other effect. In a 'multi-feed machine, at least one secondary or auxiliary feed position, in addition to the main feed position corresponding to that of a single feed machine, is provided at a spaced point on the circular locus so as to simultaneously feed a plurality of strands for active knitting on the needles during the revolution of the needle cylinder. The desire for greater production on the part of the commercial knitter in recent years has made the use of multi-feed machine increasingly attractive.

In the knitting on multi-feed circular machines of articles where back-and-front knitting is involved, as in forming the heel and toe of hosiery, it is the yarn at the main feed position that remains in action during the periods of back and forth knitting, the yarns from the secondary feed position or positions being disengaged until operation in the normal direction is resumed. During these periods, the main feed yarn, of course, oscillates back-and-forth across the mouth of the channel of the throat plate as the needle cylinder changes direction. As the design of my earlier patent above identified furnishes wear-resistant ceramic material across the entirety of the 3,392,549 Patented July 16, 1968 yarn-engaging edge of the plate, it is ideally suited for service at the main feed position.

However, in at least certain commercial multi-feed machines, such as that known in the art as the Singer- Fidelity, the location of the secondary feed position coincides with a point on the needle path where the needles are in elevated position, allowing the latches of the needles to swing outwardly under the action of centrifugal force as the cylinder rotates at high speed. The

disposition of the throat plate at the secondary position is such that the lower surface of the plate is engaged by the latches when swung out as just described. This rubbing contact between the needle latches and the throat plate undersurface is not especially objectionable so long as the undersurface of the plate is steel, giving steel-tosteel contact. However, if a throat plate modified in accordance with my prior patent is mounted at the secondary feed position, steel-to-ceramic contact results, the consequence of which is severe wear in a relatively short period of the needle latches, requiring replacement by new needles.

In addition to the excessive wear on the needle latches as just described, the provision of wear-resistant ceramic material across the full expanse of the throat plate as afforded in my prior design is unnecessary for the needs of the secondary feed position plate. At the secondary position, the yarn does not oscillate across the face of the plate since it does not enter into back and forth knitting but remains essentially constantly at one corner of the plate, arising from that corner when the feed fingers are taken out of action and returning thereto when the feed fingers are restored to operative position and tension is imposed on the yarn. Consequently, the wear on the throat plate at the secondary position is concentrated at one of its corners and, other than at this corner, the ceramic material serves no significant function and merely adds unnecessarily to the cost of the plate.

The principal object of the present invention is, therefore, a throat plate for knitting machines provided with an insert of wear-resistant ceramic material at the normal running position of the yarn thereon.

Another object of this invention is a throat plate having a wear-resistant ceramic insert mounted at a corner of the plate, the joints between the insert and the body of the plate being so constructed as to permit the yarn to move freely onto and off the insert as required for operation of the machine without tending to become snagged or trapped in the joint.

These and other objects of the present invention will be revealed in full detail by the annexed drawings when read in conjunction with the following detailed description in which:

FIG. 1 is a top plan view looking down on a conventional throat plate equipped with an insert in accordance with the present invention;

FIG. 2 is a front elevation of the plate of FIG. 1;

FIG. 3 is a vertical cross-section taken substantially along line 3-3 of FIG. 1;

FIG. 4 is an enlarged detail view of a fragment of FIG. 2;

FIG. 5 is a diagrammatic perspective view showing a plate as in FIG. 1 in operative association with a typical yarn feed finger and the needles of the knitting machine; and

FIG. 6 is a view similar to FIG. 4 of a modified embodiment of the invention.

Turning now to a detailed description of the invention as illustrated in FIGS. 15, the numeral 10 is used to generally designate the throat plate which, except as hereinafter indicated, may be of any conventional design known in the art. Typically, such a plate, as is readily apparent from the drawings, takes the form of a fairly fiat, generally rectangular block-like member, usually machined out of steel or the like. One side face 12 of this element (which serves as the front face when the plate is oriented in its conventional operative position) is shaped with a shallow convex curvature so as to conform generally with the curvature of the cylinder of the knitting machine with which the plate is to be utilized. The upper portion of the arcuate side 12 may be, and ordinarily is, slightly beveled as indicated at 14. In the top face 16 of the element is a channel 18, of generally U-shaped cross-sectional configuration, extending from the front side 12 to the opposite or rear side 20. Channel 18 extends in depth well over one-half of the thickness of the block-like element and is defined by a bottom wall 22 and two opposite, upstanding side walls 24 and 26. In the flange-like portions flanking channel 18, there are provided holes 28, 28 for attaching the throat plate into the operative position on the undersurface of the latch ring of the knitting machine and these holes 28, 28 are preferably elongated in a direction parallel to channel 18 to facilitate precise radial adjustment of the front face of the plate. Dependent upon the type of circular knitting machine with which the plate is to be associated, a transversely elongated aperture may be formed in bottom wall 22 of channel 18 somewhat nearer front side 12 than rear side 20, as indicated in the drawings at 30, or bottom wall 22 may be left solid.

Up to this point, the description has dealt with only those features conventional to throat plates known in the art. In accordance with the present invention, a recess is cut into the front face 12 of the plate element at the elbow or junction between the side wall 24 and bottom wall 22 of U-shaped channel 18. The shape of the recess, designated 32, is not crucial significance, so long as it extends a distance in a transverse direction along bottom wall 22 as well as side wall 24 substantially in excess of the thickness of the yarn to be knitted. For example, as shown in the drawings, the insert 32 may have the shape in vertical cross-section of a sector of a circle equal approximately to three quadrants, the fourth quadrant corresponding to the void defined by channel 18. Such configuration is particularly convenient since the recess can be formed by means of a drill, although other configurations are equally suitable in principle.

Mounted within recess 32 is an insert 34 of such configuration and dimensions as to mate as closely as practicable with the recess. Insert 34 is formed of wear-resistant ceramic material, of the type hereinafter defined. The depth of recess 32, i.e. its entent axially of channel 18, is so selected as to provide a secure anchorage for the insert, which is to say that recess 32 should be at least long enough to keep insert 34 from readily slipping out. If sufficiently close to tolerances can be achieved, the insert will remain within the recess without the need for further measures as there are little or no forces arising during operation of the machine which tend to cause the insert to become dislodged. However, if an even more permanent grip on insert 34 is desired, use can be made of any good adhesive cement known in the art.

It will be seen from the drawings, especially FIG. 4, that insert 34 is so notched or cut away as to provide surfaces serving as continuations of bottom wall 32 and side Wall 34 of U-shaped channel 18. It is an important feature of the present invention, however, that the insert surfaces corresponding to the aforesaid channel walls do not extend in precisely coplanar relationship with those walls. Rather, the insert surface designated 36, corresponding the bottom wall 22, is at least in the region adjacent its juncture with surface 22, slightly depressed below the plane of that surface. Similarly, the certical surface, designated 38, corresponding to surface 24 of the channel, is, at least in the region adjacent its juncture with surface 24, slightly elevated above the plane of. the surface 24. The extent of depression and elevation, respectively, of the two surfaces need only be quite small, say a few thousandths of an inch, so that the yarn moving onto surface 36 from surface 22 and onto surface 24 from surface 38, in the course of the operation of the machine, hereinafter to be described, will slide smoothly across the joints between the respective pairs of surfaces without encountering any serious tendency to be engaged or trapped in such joints. In order to provide a different characterization of the relationship of the pairs of surfaces in question, using an insert of symmetrical configuration as shown in FIG. 4 having an approximate diameter of inch, rotation of the insert about its own axis approximately 5 will provide the requisite extent of depression and elevation for the surfaces 36 and 38, respectively.

The axis of an insert so configured being arranged to coincide with the axis of intersection of surfaces 22 and 26, it follows that the quantitative extent of elevation and depression decreases along the surfaces as that axis is approached. If desired, a greater area of the insert surfaces can coincide with the planes of the corresponding channel surfaces so long as the requisite relationship exists in the regions of the joints therebetween.

It will be understood that the maximum extent of depression and elevation, respectively, will largely depend upon practical considerations, such as the balance between the need for preserving substantial structural strength in the bottom wall of the channel beneath the insert and the need for providing a substantial thickness of wear-resistant material at the corner to receive the wear of the yarn. In the case of the vertical insert surface 38, that surface cannot project so far outside the channel surface as, on the one hand, to substantially eliminate the horizontal surface 36 or, on the other hand, to produce a notch from which the yarn would have difiiculty in leaving upon upward movement. In general, it is preferred that the planes of the inert surfaces lie sufliciently close to the planes of their corresponding channel surfaces as to minimize the disturbance imparted to the yarn in moving across the respective joints but at the same time to insure that the surface onto which the yarn passes, i.e. the downstream surface in the direction of yarn movement, will be sufficiently lower than the upstream surface as to eliminate the likelihood of the yarn becoming snarled or snagged in the joint. With these guidelines, one skilled in the art should have no difficulty in selecting specific arrangements that will satisfy the needs of the invention.

Where the path of the yarn leaving the throat plate is such that the yarn passes from the mouth of the channel in a direction having an appreciable downward component, it will be apparent that the front face 40 of the insert 34 cannot project beyond the plane of the front face 42 of the plate 10. Otherwise, a sharp edge would be presented that would damage the yarn. For this reason, the front face of the insert is at least flush with the front face of the plate and, preferably is very slightly recessed inwardly thereof.

The function of the insert as described in connection with FIGS. 1-4 will become somewhat clearer from a consideration of FIG. 5. FIG. 5 is a diagrammatic perspective view of the throat plate modified as in FIGS. 1-4 in operative position at the auxiliary feed point of the knitting machine, all parts of which with the exception of a fragment of a yarn carrier finger and a few of the knitting needles are omitted for sake of clarity. As has already been mentioned briefly, in contrast to the main feed position where the yarn is normally caused to oscillate back and forth, at some period during the over-all knitting cycle, the yarn at the auxiliary feed point moves constantly in one direction during the time it is engaged in active knitting. Thus, with the needle cylinder rotating in a counter-clockwise direction indicated by the arrow adjacent the needles N, the yarn designated Y remains at the corner defined by the intersection of front side 12 and channel walls 22, 24, where the insert 34 is mounted. Obviously, if the needle cylinder normally rotated in the opposite or clockwise direction, the opposite corner of the channel would be selected at the point for the provision of the insert.

A necessary incident to the operation of a multi-feed machine is periodic engagement in and disengagement from the knitting operation of the yarn being fed at the auxiliary feed point. As shown in -FIG. 5, the yarn of feed finger F is in normal operative position with the yarn flowing through the feed opening therein angularly to the corner as just described and thence downwardly and angularly to the revolving array of knitting needles N. When the auxiliary yarn is to be disengaged from knitting, the feed finger -F is moved by mechanical instrumentalities conventional to the knitting machine and forming no part of the present invention to a position of considerable elevation with respect to the throat plate. The yarn, of course, shares in this movement to the extent permitted by the tension therein, sliding upwardly out of the corner along the front edge of insert surface 38 and thence along the front edge of channel surface 24 until displaced entirely away from the throat plate. Thereafter, when the auxiliary yarn is again to be introduced into knitting, the feed finger F drops back into operative position and upon reengagement of the auxiliary yarn with the knitting needles, the yarn is pulled across the front edge of channel wall 22 into the corner reinforced by insert 34. When the cyclical path of movement of the yarn during the several phases of the knitting operation is understood, significance of the critical relationship of the insert surfaces is more readily comprehended.

The ceramic material from which the insert of this material is constructed is very commonly known in the art at the present time. One satisfactory ceramic may consist of the type of ceramic material which is described in US. Patent No. 2,369,266 to Thurnauer, issued Feb. 13, 1945. It is not necessary, however, that the ceramic have the electrical properties therein described, although these may be desirable in some instances. Ceramics having properties satisfactory for the manufacture or inserts according to this invention may be identified by the following characteristics:

A wide line of suitable ceramic materials of varying chemical constituency as wellas mechanical properties are sold by the American Lava Corporation under the trade name AlSiMag and a number of technical bulletins describing the variety of products that can be obtained from the company, of which special mention can be made of Bulletins Nos. 624 and 622. U.S. Patent No. 2,214,703 to Thurnauer also describes ceramic material satisfactory for the purposes of the present invention.

Although, the use of an insert having the configuration of a sector of a circle offers certain advantages, particularly from a manufacturing standpoint, principally among which is the case of forming the recess in the plate as well as the insert itself, the invention is not confined to this one configuration. One example of a suitable alternative appears in FIG. 6. In this modified embodiment the recess 32' is in the shape of an elbow having arms of generally equal length, While the insert 34 is of appropriate mating configuration. The remainder of the plate in the modified embodiment is unchanged from the main embodiment. Other forms will, of course, be apparent to one skilled in this art.

In lieu of wear-resistant ceramic material of the type already mentioned, certain extremely hard metallic alloys can be employed with useful results. Examples of such alloys include Carbaloy, Tantaloy and Itellite, while the durability of these substitute materials is not as outstanding as the preferred ceramics, they have sufiicient performance life as to be acceptable under many circumstances.

Where words of orientation such as front and rear, top, back, depressed, elevated and the like have appeared in the aforegoing specification, such usage is intended to be for purposes of description only and not by way of limitation since they are obviously relative to the orientation of the machine as a whole or some other points of reference.

Having thus described the invention, that which is claimed is:

1. A throat plate for knitting machines comprising a base member having therein a U-shaped channel terminating in a thread-bearing edge, the yarn during knitting normally passing over said edge at one corner of said channel, said base member having a recess formed therein at said corner extending inwardly from said edge and outwardly from said corner along the adjacent faces of said channel; and an insert of wear-resistant ceramic material disposed within said recess, said insert having surfaces generally coinciding with the corresponding faces of said channel, the surface corresponding to the base of the channel being depressed at least in the region immediately adjacent the base below the plane of the base while the surface corresponding to the wall of the channel is elevated above the plane of that wall at least in the region immediately adjacent the wall.

2. The throat plate of claim 1, wherein said insert has the configuration in cross-section of the sector of a circle.

3. In a yarn guide comprising a metallic base member having an exterior surface thereon for engagement by the running yarn, said surface being cut away to provide a recess at the major point of wear by the yarn, said recess being defined by at least one edge of said surface, and an insert of wear-resistant ceramic material embedded in said recess and having an exterior surface generally continuous with the exterior surface of said base member adjacent said recess, said insert exterior surface having at least one side edge abutting along a line with the side edge of said member surface defining said recess and wherein during operation said yarn slides bodily in a direction laterally of its length across said line of abutment moving from engagement with said member exterior surface into engagement with said insert exterior surface, the improvement in which the edge of said insert exterior surface at said line of abutment is depressed slightly below the edge of said member exterior surface thereat whereby the tendency of said yarn to become caught at said line of abutment in sliding thereover is reduced.

4. In a yarn guide as in claim 3 wherein said member surface has a second edge in generally opposed relation to said first edge for defining said recess, said insert exterior surface has a second edge in generally opposed relation to said first edge thereof, said second edge of said insert surface abutting along a line with said second edge of said member exterior surface and in which during operation the yarn also slides bodily across said second line of abutment moving from engagement with said insert surface into engagement with said member surface, the further improvement in that the second side edge of said insert surface at said second line of abut ment is elevated slightly above the second edge of said member surface at said second line of abutment to reduce the tendency of said yarn to become caught at said second line of abutment.

(References on following page) References Cited UNITED STATES PATENTS Porter et a1. 242157 McKinley 66-125 Hoefer 66--12S Spiney 66-125 X Mahter et a1. 66-125 McDonough 6612S Smith 66-125 8 FOREIGN PATENTS 6/1963 Great Britain.

OTHER REFERENCES MERVIN STEIN, Primary Examiner.

RONALD FELDBAUM, Assistant Examiner. 

1. A THROAT PLATE FOR KNITTING MACHINES COMPRISING A BASE MEMBER HAVING THEREIN A U-SHAPED CHANNEL TERMINATING IN A THREAD-BEARING EDGE, THE YARN DURING KNITTING NORMALLY PASSING OVER SAID EDGE AT ONE CORNER OF SAID CHANNEL, SAID BASE MEMBER HAVING A RECESS FORMED THEREIN AT SAID CORNER EXTENDING INWARDLY FROM SAID EDGE AND OUTWARDLY FROM SAID CORNER ALONG THE ADJACENT FACES OF SAID CHANNEL; AND IN INSERT OF WEAR-RESISTANT CERAMIC MATERIAL DISPOSED WITHIN SAID RECESS, SAID INSERT HAVING SURFACES GENERALLY COINCIDING WITH THE CORRESPONDING FACES OF SAID CHANNEL, THE SURFACE CORRESPONDING TO THE BASE OF 